How to check VOC control efficiency
Coating, printing, and cleaning lines send volatile organic compounds through a control device such as a regenerative thermal oxidizer, a catalytic oxidizer, or carbon adsorption. Comparing inlet and outlet concentrations alone does not tell the whole story, because permit limits and major source thresholds are written in mass terms. This calculator reports destruction efficiency alongside hourly and annual mass emissions and two compliance checks.
Efficiency is simply (inlet - outlet) / inlet. Mass loading uses the ideal gas molar volume of 385.3 standard cubic feet per pound-mole at 68 degrees F, so lb/hr equals ppmv divided by one million, times scfm, times 60, times molecular weight, divided by 385.3. At 1,200 ppmv in, 45 ppmv out, 3,500 scfm, and toluene at 92.14, the efficiency is 96.25 percent, the inlet loading is about 60.3 lb/hr, and the outlet is about 2.26 lb/hr.
Many NESHAP and NSPS subparts under 40 CFR parts 60 and 63 require 95 or 98 percent destruction or removal efficiency, and several allow an outlet concentration such as 20 ppmv as an alternative path, which is why both checks are editable here. Annual tonnage also matters, since 10 tons per year of a single HAP or 25 tons per year combined defines a major source. Confirm the exact subpart, averaging period, and test method with your permitting authority, and have an environmental engineer review compliance demonstrations. Requirements are as in effect in September 2026.
Frequently asked questions
Parts per million by volume says nothing about mass on its own. Using the ideal gas molar volume of 385.3 standard cubic feet per pound-mole at 68 degrees F, the volumetric fraction is converted to moles and then to pounds with the molecular weight of the representative compound.
It depends on the specific standard. Many NESHAP and NSPS rules under 40 CFR parts 60 and 63 require either 95 or 98 percent destruction or removal, and several allow an outlet concentration such as 20 ppmv as an alternative compliance path. Read the subpart that applies to your source.